Geometrically enhanced magnetoresistance in ferromagnet–insulator–ferromagnet tunnel junctions

Abstract

Ferromagnetic–insulator–ferromagnetic trilayer tunnel junctions show magnetoresistance (JMR) effects of about 14% or greater at room temperature. Much larger values of the JMR (100% or more) are observed when the actual tunneling resistance (RT) is comparable to electrode film resistance (RL) over the junction area. This latter apparent JMR is an artifact of the nonuniform current flow over the junction in the cross geometry of the electrodes. The ferromagnetic films were CoFe and Co or Ni0.8Fe0.2, and the tunnel barrier was AlN or Al2O3. These junctions show nonvolatile memory effects. The geometrically enhanced large JMR in junctions can be effectively used as magnetic sensors and memory elements.